CB750 K2- How Delightfully Old School.

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desertrefugee
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Re: CB750 K2- IT LIVES!!!! (Now with 100% more video)

Post #91 by desertrefugee » Wed Oct 18, 2017 8:08 pm

Now THAT is sweet. Reminds me of my old SOHC. Miss that bike. Lotta memories there. Congratulations on that score.
'97 Valkyrie, '86 VMax Project, '79 CBX-Z, '78 GL1000, '83 Voyager Lite Project, '78 750F BIG Project, '74 750K HUGE Project

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Lucien Harpress
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Re: CB750 K2- IT LIVES!!!! (Now with 100% more video)

Post #92 by Lucien Harpress » Fri Oct 20, 2017 5:49 pm

...I hate this bike. So very very much.

You see, I spent quite a bit of money on my other rides. More than I'd like to admit. And while they run quite well most of the time, they also fought me every step of the way. Simple procedures were either overcomplicated by me or by circumstances, and ended up accomplishing nothing. They run, but just barely. And the less said about my KZ1300, the better.

But this **** CB750. Bought it for 300 bucks, sitting outside for 20 years, with nothing but some spray paint, another $200 parts bike, and some choice pieces here and there-

AND THIS CUSSED THING RUNS BETTER THAN EVERYTHING ESLE!!!!!!!

Seriously though. I checked the sync on it, and two of the carbs were slightly off. Half a turn on one, quarter turn on the other, and the idle settles right down to 1.5K and STAYS there. Revs up butter-smooth from idle to (near) redline, and drops right back down, pretty as you please.

[sigh]

I was going to sell this thing, too. NOW I've got to put enough money into it to get it roadworthy. Son of a gun.
1969 CT90- Needs rear tube and possibly rings
1976 GL1000 (Yellow)- Carb Shenanigans.
1984 GL1200 Standard- For Sale!
1980 KZ1300- Carb balancing when the weather warms up
1972 CB750 Barn Find- Tires and Head Bearings

All advice I give is only valid until an expert corrects me.

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Re: CB750 K2- IT LIVES!!!! (Now with 100% more video)

Post #93 by CYBORG » Fri Oct 20, 2017 5:56 pm

Congratulations . Its a never ending pursuit,......but great when it all comes together
1978 custom GL1000
1977 custom with 1200 engine
1985 gl1200

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Re: CB750 K2- IT LIVES!!!! (Now with 100% more video)

Post #94 by JSBail » Fri Oct 20, 2017 6:00 pm

I know what you mean. I never seem to have a problem spending money on my 750 to make it even better. Right now it needs a paint job but I just can't get motivated to do it because I want to strip it down to the bare frame. And when ever I find a reason to split the cases on the engine again (and I'm sure I will) the trans will get treated to back cut gears.
Scott

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Lucien Harpress
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Re: CB750 K2- Do NOT Try This At Home

Post #95 by Lucien Harpress » Wed Nov 01, 2017 7:04 pm

So.... yeah. I'm only posting this photo because it's AFTER the ride, and I'm not dead. I present: the jankiest setup on two wheels.

20171101_175859.jpg


So.... IV bottle gas tank, no front brake, no tail light, one blinker, and no mirrors. I put all of about 1/4 mile into it, and... here's my breakdown.

The Good:
-Clutch works. Very nicely actually- dropping from neutral to 1st is more like a click, vs. a KACHUNK.
-On acceleration, everything sounds... normal.
-It goes down the road straight!

The Bad:
-Ride is.... not great. A bit of (real light) bouncing on the front end, which may be forks need rebuilding (they do).
-Lots of sharp popping from.... somewhere. It might be cylinder 1 again, which might be the plug wire.
-Every time I decelerated, the motor died. Not quite exactly sure why yet.
-It starts REALLY hard. Like.... full choke will get it to hit, then die. Letting the choke off helps a bit, but it will eventually die there, too. Granted it was pretty cold out, but to warm it up I pretty much had to hold the throttle slightly open until it was warm enough to settle down on its own.

ANYWAY- this gets me something to work with. Next up- tank cleaning. Gonna try some electrolysis!
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1969 CT90- Needs rear tube and possibly rings
1976 GL1000 (Yellow)- Carb Shenanigans.
1984 GL1200 Standard- For Sale!
1980 KZ1300- Carb balancing when the weather warms up
1972 CB750 Barn Find- Tires and Head Bearings

All advice I give is only valid until an expert corrects me.

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Re: CB750 K2- Do NOT Try This At Home

Post #96 by JSBail » Wed Nov 01, 2017 7:24 pm

Lucien Harpress wrote:
-Lots of sharp popping from.... somewhere. It might be cylinder 1 again, which might be the plug wire.
-Every time I decelerated, the motor died.



Check your idle mixture screws. My son's K3 popped a bunch and sometimes died on decell and it turned out he had the idle mixture screws backed way out (too lean). I can't remember at the moment how many turns out they should be but once I had them set it was all good. You may also want to pull your points cover off while it's running and see if the points arc arcing real bad, if so then it could be a bad condensor and they'll make the engine pop loud too. As far as the front end bouncing, what condition is the front tire in? Any signs of dry rot or cracking?

EDIT: And another thing, there's no fast idle cam for the choke so they can be cold blooded when started cold as in you have to play with the throttle sometimes till it warms up a bit but should only need the choke on a cold start, it should start easily without it once warmed.
Scott

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Lucien Harpress
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Re: CB750 K2- Do NOT Try This At Home

Post #97 by Lucien Harpress » Wed Nov 01, 2017 7:51 pm

I was wondering about the mixture screws. I fiddled with it a bit earlier in the year, but I don't want to lock anything down until I replace the coils. While the coils themselves spec out, the plug wires are pretty trashed. Like, no rubber left at all- you touch it, it just crumbles. Once I eliminate poor contact at the plug caps, then I'll move on to carb tuning (which will hopefully be easier with 4 individual exhausts). Good call on the condenser, though. It only seems to be popping out the one pipe though, so we'll see.

As for the front tire... old? Dry-rotted? Cracking?

How about "Yes, to all of the above"? O_o' The tires are really only good for rolling it around the yard. They'll get replaced once a few other things get ironed out (clean tank, correct length throttle cable, etc.)
1969 CT90- Needs rear tube and possibly rings
1976 GL1000 (Yellow)- Carb Shenanigans.
1984 GL1200 Standard- For Sale!
1980 KZ1300- Carb balancing when the weather warms up
1972 CB750 Barn Find- Tires and Head Bearings

All advice I give is only valid until an expert corrects me.

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Re: CB750 K2- Do NOT Try This At Home

Post #98 by Easter » Wed Nov 01, 2017 9:02 pm

Even with the IV bottle and the split seat, it is looking pretty good.
Bikes at present:
80 GL1100 Interstate: Now a Cafe Racer called DRAGON WING.
81 GL1100 collecting dust with about 300,000 miles, known as BLACK BEAUTY
2008 (I think) GL1800 Nice bike but as exciting as the family sedan!
76 GL1100 yes, 1100 with 1000 heads and cams, being customized
A fleet of parts bikes awaiting resuscitation or customization or abandonment :IDTS:

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Lucien Harpress
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Re: CB750 K2- Do NOT Try This At Home

Post #99 by Lucien Harpress » Wed Nov 01, 2017 9:43 pm

Speaking of the seat, I'm not sure what I want to do with it yet. A new cover is a must, but I was hoping to save the foam. Problem is, some mouseys made a nest in the back, so there's a giant void in the passenger section. The "right" thing to do would be to replace the foam with something new, but I'm wondering how difficult it would be to just fill in that section.

Musings for another day, I suppose.
1969 CT90- Needs rear tube and possibly rings
1976 GL1000 (Yellow)- Carb Shenanigans.
1984 GL1200 Standard- For Sale!
1980 KZ1300- Carb balancing when the weather warms up
1972 CB750 Barn Find- Tires and Head Bearings

All advice I give is only valid until an expert corrects me.

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Re: CB750 K2- Do NOT Try This At Home

Post #100 by robin1731 » Thu Nov 02, 2017 10:34 am

Mixture screws factory setting is one turn out.

.
1975 GL1000 parts bike (parts for sale)
1976 Goldwing Super Sport
1985 Honda Elite
1976 KZ900 Dragbike
1992 ZX7 Dragbike (KZ900 style motor w/NOS)
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Re: CB750 K2- One More Issue for the List

Post #101 by Lucien Harpress » Tue Dec 19, 2017 9:16 pm

Because it's winter for me (with no heat in the barn), bike projects have kind of wound down. However, I was able to learn some valuable information about the gas tank after a long soak in evaporust- namely the gas tank is trashed. I'm getting a couple of pinhole leaks in the back corners- I'm guessing the evaporust blasted through enough of the crap inside the tank to reach the outside. I realize I could probably coat the tank and be done with it, but given the fact the inside still looks pretty trashed, this is probably the first leak among many. As I was going to get it repainted anyway, I'm not out much.

So, after I get my tax returns and pay off some dental fillings, it's off to find a tank that's at least solid and (surprisingly enough) the mounts for the emblems aren't filled in, for preferably under 100 bucks. There's a couple of ebay hits, but this is way too soon to be shopping for them.

In the meantime, I may try to free up all the (frozen) front brake parts, and see if any of that is still usable.
1969 CT90- Needs rear tube and possibly rings
1976 GL1000 (Yellow)- Carb Shenanigans.
1984 GL1200 Standard- For Sale!
1980 KZ1300- Carb balancing when the weather warms up
1972 CB750 Barn Find- Tires and Head Bearings

All advice I give is only valid until an expert corrects me.

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luludog
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Re: CB750 K2- One More Issue for the List

Post #102 by luludog » Wed Dec 20, 2017 7:24 am

I’ve got the seat foam off a ‘72 CB350. Need to find it, but maybe you can graph a piece of it onto the 750 foam. Also have used carburetor parts, let me know if you need something (free).
-Ray

1977 GL1000 - http://www.ngwclub.com/forum/viewtopic.php?f=30&t=40398
1975 CB750K5 - stock restoration http://www.ngwclub.com/forum/viewtopic.php?f=13&t=40426
1971 CB175K5 - stock restoration http://www.ngwclub.com/forum/viewtopic. ... 95&start=0
1972 CB350 - resto-mod cafe project http://www.ngwclub.com/forum/viewtopic.php?f=30&t=47429
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desertrefugee
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Re: CB750 K2- One More Issue for the List

Post #103 by desertrefugee » Wed Dec 20, 2017 11:51 am

Lucien, as rabid a bike guy as you are, how tough would it be to tack up some Visqueen to seal the biggest holes in your barn workspace and light off a kerosine heater? (I know, easy for me to say when a cold night in the desert is 35F, but just asking). Might not be suitable for Jan-Feb, but Oct/Nov, March/April maybe?

That way, the rest of us would get real reports rather than frustrated musings... :cry:
'97 Valkyrie, '86 VMax Project, '79 CBX-Z, '78 GL1000, '83 Voyager Lite Project, '78 750F BIG Project, '74 750K HUGE Project

"Motorcycling is not, of itself, inherently dangerous. It is, however, extremely unforgiving of inattention, ignorance, incompetence or stupidity." - Anonymous

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Lucien Harpress
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Re: CB750 K2- One More Issue for the List

Post #104 by Lucien Harpress » Wed Dec 20, 2017 6:08 pm

Honesty? Kind of a PITA. I've got this weird combination of a couple pretty large spaces that (due to having to share with both my parents and a couple of my siblings) have a LOT of stuff in them. My 4 main bikes are in a one-car garage, so I have just enough space to squeeze around them, and that's about it. Because of this, most of my major work is done in the driveway, which is a big no-no when there's ice and snow all over it. ESPECIALLY since my lightest bike starts at 500 lbs. and they just go up from there.....

I've tried it once or twice, and it's honestly more trouble than it's worth.
1969 CT90- Needs rear tube and possibly rings
1976 GL1000 (Yellow)- Carb Shenanigans.
1984 GL1200 Standard- For Sale!
1980 KZ1300- Carb balancing when the weather warms up
1972 CB750 Barn Find- Tires and Head Bearings

All advice I give is only valid until an expert corrects me.

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Lucien Harpress
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Re: CB750 K2-Repaint, or No?

Post #105 by Lucien Harpress » Fri May 25, 2018 10:46 pm

So I managed to find a tank on Ebay for a reasonable price. There's a bit of internal rust, but nothing too bad (especially with the build-in petcock sediment bowl- a nice touch). The most important thing is that it's solid.

I threw on the petcock, ran some lines, splashed in some gas, and took the bike for it's first ride longer than about 500 feet down the road and back. The clutch needs a minor adjustment, no suspension travel on the front makes for an interesting ride, and it's so different to ride a bike that actually has an EXHAUST note, but overall this bike runs VERY well. A bit rich on cylinder 1, which I'll confirm when I pull plugs, and it could use some new coils, but I'm getting to a point where this bike is actually getting finished.

In fact, in a couple days I'm sending the tins out to get painted, but...... I'm no so sure I should. lolol

33425471_10156140459227419_4740503031211098112_n.jpg
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1969 CT90- Needs rear tube and possibly rings
1976 GL1000 (Yellow)- Carb Shenanigans.
1984 GL1200 Standard- For Sale!
1980 KZ1300- Carb balancing when the weather warms up
1972 CB750 Barn Find- Tires and Head Bearings

All advice I give is only valid until an expert corrects me.


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